1. Field of the Invention
The present invention relates generally to pluggable converter module subassemblies, and more particularly, to pluggable electrical and optical converter modules configured to interface with video systems.
2. Description of Related Art
Conventional optoelectronic transceiver modules are utilized to interconnect circuit cards of communication links and other electronic modules or other subassemblies. Optoelectronic transceiver modules are designed to receive electrical data signals and retransmit these signals as optical signals, and vice versa. Various international and industry standards define the type of connectors used to interface computers to external communication devices, such as modems, network interfaces, and other transceivers. It is desirable to make transceiver modules pluggable so the modules can be easily exchanged. It is also desirable to miniaturize transceiver modules in order to reduce real estate usage on printed circuit boards (PCBs) and increase the port density associated with the network connection (switch boxes, cabling patch panels, wiring closets, computer I/Os, etc.).
Numerous standards are known that define form factors for miniaturized electronic devices, such as the Small Form-Factor Pluggable (SFP) standard that specifies an enclosure 9.8 millimeters in height, 13.5 millimeters in width, and a minimum of 20 electrical input/output connections. The specific standards for SFP transceivers are set forth in the “Small Form-Factor Pluggable (SFP) Transceiver Multisource Agreement (MSA),” dated Sep. 14, 2000, which is hereby incorporated by reference.
Due to current designs and specifications, conventional optoelectronic transceiver modules are not compatible with video circuitry or connectors. For example, video subassemblies typically require different connectors, such as ST or BNC connectors. Moreover, video subassemblies commonly utilize unidirectional signals, and thus do not always require a bidirectional signal interface as provided by transceiver modules. Furthermore, a conventional transceiver module can only be installed into a host device specifically designed to receive that specific transceiver module.
Additionally, a video signal typically includes pathological problems, which a conventional transceiver module would be unable to accommodate. Most transmitters in optical modules have an automatic power control (APC) circuit that keeps the optical power output at a set level. These circuits assume incoming data will have a constant average duty cycle of about 50% over a period of time. Such a time period is usually in the range of 1 millisecond (ms). Since the pathological condition may last for about 50 milliseconds, the laser driver of the optical transmitter would be adjusted too high or too low, depending upon the duty cycle of the signal. A detailed explanation of “Pathological Conditions in Serial Digital Video Systems” can be found in the publication having said title by SMPTE Engineering Guideline, Number EG 34-1999, by the Society of Motion Picture and Television Engineers approved and published Jan. 15, 1999, which is hereby incorporated by reference.
Some progress has been made in developing pluggable modules for video systems. For example, U.S. Pat. No. 7,307,847 (“the '847 patent”), entitled “Pluggable Video Module,” having a common inventor with the present application, and hereby incorporated by reference, teaches a pluggable video module having an SFP housing configuration. While the pluggable video module of the '847 patent above enables an SFP module to accommodate some video signals, the '847 patent does not disclose a new, unexpectedly smaller form factor.
Additionally, video computer systems commonly utilize removable circuit cards or printed circuit boards (PCBs) having blind mating card edge connectors that connect to receptacles mounted on a backplane of the video computer system. These removable circuit cards or PCBs can be removed or replaced to upgrade or repair existing circuitry. Conventional pluggable video modules attached to a removable PCB connected to a backplane must be manually unlatched or disconnected to remove the PCB from the backplane. Furthermore, video cables that have been connected to conventional pluggable video modules also must be manually disconnected before circuit cards or PCBs can be disconnected from a backplane.
Accordingly, there is an unmet need for a smaller, pluggable video module that requires less real estate for mounting, and moreover, enables a user to freely remove or replace an installed PCB from a backplane without having to manually unlatch attached pluggable video modules, and also without having to manually disconnect optical or electrical cables attached to the pluggable video modules before removing the PCB from the backplane.
Moreover, there is a need for a smaller pluggable solution that consumes less electrical power than conventional designs, present solution, so the use of VCSELs, in particular, single mode VCSELS, offers reduced power consumption over traditional lasers used for pluggable video modules like SFPs.
Additionally, there is a need for a pluggable video module that automatically connects to the backplane and associated optical and copper wire circuitry during installation of a PCB to a backplane.